Control of power converter based on dynamic constraint factors

ABSTRACT

A power delivery system may include a power converter configured to electrically couple to a power source and further configured to supply electrical energy to one or more loads electrically coupled to an output of the power converter, and control circuitry configured to select a constraint factor from a plurality of different constraint factors based on at least one of an input voltage to the power converter and a power level available to the power converter, and control the power converter in accordance with the constraint factor.

RELATED APPLICATION

The present disclosure claims priority to U.S. Provisional PatentApplication Ser. No. 63/058,014, filed Jul. 29, 2020, which isincorporated by reference herein in its entirety.

FIELD OF DISCLOSURE

The present disclosure relates in general to circuits for electronicdevices, including without limitation personal portable devices such aswireless telephones and media players, and more specifically, tolimiting current in a power converter.

BACKGROUND

Portable electronic devices, including wireless telephones, such asmobile/cellular telephones, tablets, cordless telephones, mp3 players,and other consumer devices, are in widespread use. Such a portableelectronic device may include circuitry for implementing a powerconverter for converting a battery voltage (e.g., provided by alithium-ion battery) into a supply voltage delivered to one or morecomponents of the portable electronic device. The power delivery networkmay also regulate such supply voltage, and isolate the downstream loadsof these one or more devices from fluctuation in an output voltage ofthe battery over the course of operation.

In addition to regulating the supply rail for the supply voltage, it maybe desirable for the power converter (or a control circuit for the powerconverter) to provide for active protection mechanisms to limit anamount of current that can be drawn by the one or more componentspowered from the supply rail.

SUMMARY

In accordance with the teachings of the present disclosure, one or moredisadvantages and problems associated with existing approaches tooperating a power converter may be reduced or eliminated.

In accordance with embodiments of the present disclosure, a powerdelivery system may include a power converter configured to electricallycouple to a power source and further configured to supply electricalenergy to one or more loads electrically coupled to an output of thepower converter, and control circuitry configured to select a constraintfactor from a plurality of different constraint factors based on atleast one of an input voltage to the power converter and a power levelavailable to the power converter and control the power converter inaccordance with the constraint factor.

In accordance with these and other embodiments of the presentdisclosure, a power converter may be configured to receive an inputvoltage from a voltage source and to generate an output voltage andoperate in a plurality of operating regions wherein a maximum currentdrawn by the power converter in each operating region of the pluralityof operating regions is defined by a constraint factor corresponding tosuch operating region.

In accordance with these and other embodiments of the presentdisclosure, a power delivery system may include a power converterconfigured to receive an input voltage from a power source and togenerate an output voltage, and control circuitry configured tocalculate a plurality of current limit values, each current limit valueof the plurality of current limit values corresponding to a constraintfactor, and control the power converter based on a current limitselected as a lowest of the plurality of current limit values.

In accordance with these and other embodiments of the presentdisclosure, a method may include, in a power converter configured toelectrically couple to a power source and further configured to supplyelectrical energy to one or more loads electrically coupled to an outputof the power converter, selecting a constraint factor from a pluralityof different constraint factors based on at least one of an inputvoltage to the power converter and a power level available to the powerconverter, and controlling the power converter in accordance with theconstraint factor.

In accordance with these and other embodiments of the presentdisclosure, a method may include receiving an input voltage from avoltage source and generating an output voltage, and operating in aplurality of operating regions wherein a maximum current drawn by thepower converter in each operating region of the plurality of operatingregions is defined by a constraint factor corresponding to suchoperating region.

In accordance with these and other embodiments of the presentdisclosure, a method may be provided in a system having a powerconverter configured to receive an input voltage from a power source andto generate an output voltage. The method may include calculating aplurality of current limit values, each current limit value of theplurality of current limit values corresponding to a constraint factorand controlling the power converter based on a current limit selected asa lowest of the plurality of current limit values.

In accordance with these and other embodiments of the presentdisclosure, a device may include one or more components, a powerconverter configured to deliver electrical energy to the one or morecomponents, and a control circuit for controlling a current associatedwith the power converter, the control circuit comprising threshold-basedcontrol circuitry configured to control the current based on at least apeak current threshold level for the current and a valley currentthreshold level for the current and timer-based control circuitryconfigured to control the current based on a duration of time that thepower converter spends in a switching state of the power converter.

Technical advantages of the present disclosure may be readily apparentto one skilled in the art from the figures, description and claimsincluded herein. The objects and advantages of the embodiments will berealized and achieved at least by the elements, features, andcombinations particularly pointed out in the claims.

It is to be understood that both the foregoing general description andthe following detailed description are examples and explanatory and arenot restrictive of the claims set forth in this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, in which like referencenumbers indicate like features, and wherein:

FIG. 1 illustrates a block diagram of selected components of a powerdelivery network, in accordance with embodiments of the presentdisclosure;

FIG. 2 illustrates an example graph of an open circuit voltage of abattery versus the battery's state of charge, in accordance withembodiments of the present disclosure;

FIG. 3 illustrates a block diagram of selected components of anequivalent circuit model for a battery, in accordance with embodimentsof the present disclosure;

FIG. 4 illustrates an example graph of a battery voltage and a batterycurrent versus time associated with a current step drawn from a battery,in accordance with embodiments of the present disclosure;

FIG. 5 illustrates a first-order model of a battery simplified to atime-varying voltage source in series with an equivalent seriesresistance, in accordance with embodiments of the present disclosure;

FIG. 6 illustrates an example graph of a maximum battery current versusan internal effective battery voltage for battery protection, inaccordance with embodiments of the present disclosure;

FIG. 7 illustrates a block diagram of selected impedances within thepower delivery network shown in FIG. 1, in accordance with embodimentsof the present disclosure;

FIG. 8 illustrates an example graph of an output power of a powerconverter versus battery current drawn by the power converter, inaccordance with embodiments of the present disclosure;

FIG. 9 illustrates an example graph of a maximum battery current versusan internal effective battery voltage for power converter stability, inaccordance with embodiments of the present disclosure;

FIG. 10 illustrates an example graph of a maximum battery current versusan internal effective battery voltage for power limit considerations, inaccordance with embodiments of the present disclosure; and

FIG. 11 illustrates an example graph of a maximum battery current versusan internal effective battery voltage for current limit considerations,in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates a block diagram of selected components of a powerdelivery network 10, in accordance with embodiments of the presentdisclosure. In some embodiments, power delivery network 10 may beimplemented within a portable electronic device, such as a smart phone,tablet, game controller, and/or other suitable device.

As shown in FIG. 1, power delivery network 10 may include a battery 12and a power converter 20 configured to convert a battery voltageV_(CELL) generated by battery 12 into a supply voltage V_(SUPPLY) usedto power a plurality of downstream components 18, wherein eachdownstream component 18 may draw a respective current I_(LOAD1),I_(LOAD2), I_(LOAD3), etc., from the output of power converter 20,meaning an aggregate load current I_(LOAD)=I_(LOAD1)+I_(LOAD2)+ . . .+I_(LOADN) may be generated by power converter 20. Power converter 20may be implemented using a boost converter, buck converter, buck-boostconverter, transformer, charge pump, and/or any other suitable powerconverter. Downstream components 18 of power delivery network 10 mayinclude any suitable functional circuits or devices of power deliverynetwork 10, including without limitation other power converters,processors, audio coder/decoders, amplifiers, display devices, etc.

As shown in FIG. 1, power delivery network 10 may also include controlcircuitry 30 for controlling operation of power converter 20, includingswitching and commutation of switches internal to power converter 20. Inaddition, as described in greater detail below, control circuitry 30 mayalso implement active protection mechanisms for limiting currentI_(CELL) drawn from battery 12.

As of the filing date of this application, lithium-ion batteries aretypically known to operate from 4.2 V down to 3.0 V, known as an opencircuit voltage V_(OC) of the battery (e.g., battery 12). As a batterydischarges due to a current drawn from the battery, the state of chargeof the battery may also decrease, and open circuit voltage V_(OC) (whichmay be a function of state of charge) may also decrease as a result ofelectrochemical reactions taking place within the battery, as shown inFIG. 2. Outside the range of 3.0 V and 4.2 V for open circuit voltageV_(OC), the capacity, life, and safety of a lithium-ion battery maydegrade. For example, at approximately 3.0 V, approximately 95% of theenergy in a lithium-ion cell may be spent (i.e., state of charge is 5%),and open circuit voltage V_(OC) would be liable to drop rapidly iffurther discharge were to continue. Below approximately 2.4V, metalplates of a lithium-ion battery may erode, which may cause higherinternal impedance for the battery, lower capacity, and potential shortcircuit. Thus, to protect a battery (e.g., battery 12) fromover-discharging, many portable electronic devices may prevent operationbelow a predetermined end-of-discharge voltage V_(CELL-MIN).

FIG. 3 illustrates a block diagram of selected components of anequivalent circuit model for battery 12, in accordance with embodimentsof the present disclosure. As shown in FIG. 3, battery 12 may be modeledas having a battery cell 32 having an open circuit voltage V_(OC) inseries with a plurality of parallel resistive-capacitive sections 34 andfurther in series with an equivalent series resistance 36 of battery 12,such equivalent series resistance 36 having a resistance of R₀.Resistances R₁, R₂, . . . R_(N), and respective capacitances C₁, C₂, . .. , C_(N) may model battery chemistry-dependent time constants τ₁, τ₂, .. . , τ_(N), that may be lumped with open circuit voltage V_(OC) andequivalent series resistance 36. Notably, an electrical node depictedwith voltage V_(CELL-EFF) in FIG. 3 captures the time varying dischargebehavior of battery 12, and battery voltage V_(CELL) is an actualvoltage seen at the output terminals of battery 12. Voltage V_(CELL-EFF)may not be directly measurable, and thus battery voltage V_(CELL) may bethe only voltage associated with battery 12 that may be measured toevaluate battery state of health. Also of note, at a current draw ofzero (e.g., I_(CELL)=0), battery voltage V_(CELL) may be equal tovoltage V_(CELL-EFF) which may in turn be equal to an open circuitvoltage V_(OC) at a given state of charge.

FIG. 4 illustrates example graphs of battery voltage V_(CELL) andbattery current I_(CELL) versus time associated with a current stepdrawn from battery 12, in accordance with embodiments of the presentdisclosure. As shown in FIG. 4, in response to a current step event,battery voltage V_(CELL) may respond to the step, as the response curvefor battery voltage V_(CELL) experiences an initial instantaneous drop(e.g., due to equivalent series resistance 36) and time-dependentvoltage drops due to time constants τ₁, τ₂, . . . , τ_(N). Open circuitvoltage V_(OC) and the various impedances R₀, R₁, R₂, . . . R_(N), maybe a function of state of charge of battery 12, thus implying that atransient response to a new, fully-charged battery could besignificantly different from that of an aged, partially-dischargedbattery.

In operation, control circuitry 30 may determine a maximum batterycurrent I_(CELL) that may be drawn from battery 12 at any given instantbased on one or more constraints, including protection of battery 12,stability of power converter 20, and/or limitations associated withpractical limitations.

A first constraint that may be imposed by control circuitry 30 isbattery-imposed limitations for the maximum of battery current I_(CELL).To illustrate application of this constraint, FIG. 5 illustrates afirst-order model of battery 12 simplified to a time-varying voltagesource 38 with voltage V_(CELL-EFF) in series with equivalent seriesresistance 36 having a resistance value of R₀, in accordance withembodiments of the present disclosure. A maximum battery currentI_(CELL-MAX) that battery 12 may be capable of delivering may bedirectly dependent on equivalent series resistance 36. Battery currentI_(CELL) must pass through equivalent series resistance 36, which mayreduce battery voltage V_(CELL) from voltage V_(CELL-EFF) by an amountequal to resistance R₀ multiplied by battery current I_(CELL) (e.g.,V_(CELL)=V_(CELL-EFF)—R₀I_(CELL)). Perhaps more significantly, batterycurrent I_(CELL) flowing through equivalent series resistance 36 maycause power dissipation within battery 12 that is equal to resistance R₀multiplied by the square of battery current I_(CELL) (e.g., P=R₀I_(CELL)²). At high rates of discharge, battery current I_(CELL) may lead tosignificant heating within battery 12. The requirement discussed abovethat battery voltage V_(CELL) must remain above end-of-discharge voltageV_(CELL-MIN) sets a limitation on maximum battery current I_(CELL-MAX),as given by:

$I_{{CELL} - {MAX}} = \frac{V_{{CELL} - {EFF}} - V_{{C{ELL}} - {MIN}}}{R_{0}}$

Accordingly, maximum battery current I_(CELL-MAX) may be a function ofvoltage V_(CELL-EFF), assuming only battery-imposed limitations, and maybe plotted as illustrated by line CON1 shown in FIG. 6.

To enforce such limitation, control circuitry 30 may implement an activeprotection scheme to ensure that end-of-discharge voltage V_(CELL-MIN)is not violated, despite transient loads on power converter 20, so as toavoid damage to battery 12. For example, control circuitry 30 may beconfigured to monitor battery voltage V_(CELL) at terminals of battery12 and vary maximum battery current I_(CELL-MAX) drawn by powerconverter 20 as shown by constraint CON1 in FIG. 6 in order to ensurebattery 12 is not over-discharged to pushed beyond its safe operatingrange, in order to extend life of battery 12. However, complicating suchcontrol of maximum battery current I_(CELL-MAX) is that the transientresponse of battery 12 may be a function of multiple time constants(e.g., τ₁, τ₂, . . . , τ_(N)) as described above, and it may beunfeasible or uneconomical to measure such time constants for a givenbattery and vary maximum battery current I_(CELL-MAX) in a feedforwardmanner Thus, as further described below, control circuitry 30 mayimplement a negative feedback control loop around power converter 20that may monitor battery voltage V_(CELL) and vary maximum batterycurrent I_(CELL-MAX) to maintain battery voltage V_(CELL) at a desiredtarget value.

In addition to limiting current to provide for protection of battery 12as described above, it may also be desirable to limit current to providestability for power converter 20, in order to operate beyond a maximumpower point into a region of instability of power converter 20, asdescribed in greater detail below. To illustrate, reference is made toFIG. 7, which depicts a detailed block diagram of selected impedanceswithin power delivery network 10 shown in FIG. 1, in accordance withembodiments of the present disclosure. As shown in FIG. 7, powerdelivery network 10 may be modeled with battery 12 as shown in FIG. 5 inseries with a trace resistor 52, a current sense resistor 54, animpedance 56 to model equivalent losses in power converter 20, and aload 58 representing the aggregate of downstream devices 18. Traceresistor 52 may have a resistance R_(TRACE) representing a resistance ofelectrical conduit between battery 12 and power converter 20 (e.g., aconnector, printed circuit board trace, etc.). Sense resistor 54 mayhave a resistance R_(SNS) and may be used to sense battery currentI_(CELL) based on a voltage drop across sense resistor 54 and resistanceR_(SNS) in accordance with Ohm's law. Impedance 56 may model lossesinside power converter 20 with resistance R_(LOSS). After accounting forpower losses occurring in these various impedances, power converter 20may deliver output power P_(OUT) to load 58, given as:

P _(OUT) =I _(CELL) V _(CELL-EFF) −I _(CELL) ² R _(TOT)

where

R _(TOT) =R ₀ +R _(TRACE) +R _(SNS) +R _(LOSS)

For a given total resistance R_(TOT) and given voltage V_(CELL-EFF),there may exist a maximum power P_(MAX) for output power P_(OUT) ofpower delivery network 10 as a function of battery current I_(CELL) thatoccurs at a current I_(PMAX), as shown in FIG. 8, where current I_(PMAX)may be given by:

$I_{PMAX} = \frac{V_{{CELL} - {EFF}}}{2R_{TOT}}$

Thus, it is shown from FIG. 8 that power delivery system 10 will operatewith optimum power efficiency and stability if I_(CELL)<I_(PMAX), andwill operate in a region of instability (negative slope of output powerP_(OUT) versus battery current I_(CELL)) when I_(CELL)>I_(PMAX). Thismaximum allowable current I_(PMAX) may be plotted as shown in FIG. 9 asconstraint CON2 superimposed over constraint CON1 for maximum batterycurrent I_(CELL-MAX) depicted in FIG. 6. Because total resistanceR_(TOT) is greater than equivalent series resistance R₀, it may beevident that the slope of constraint CON1 is steeper than the slope ofconstraint CON2. On extrapolation, the line of constraint CON2 mayintercept the horizontal axis of voltage V_(CELL-EFF) at 0 V, which isnot shown in FIG. 9, as many batteries (e.g., lithium-ion batteries)will not be allowed to drop to such magnitude.

For high-efficiency power converters, impedance 56 may be negligiblecompared to equivalent series resistance 36, trace resistor 52, andsense resistor 54, such that total resistance R_(TOT) may be rewrittenas:

R _(TOT) ≈R ₀ +R _(TRACE) +R _(SNS)

As battery 12 is discharged with use, equivalent series resistance 36may increase and voltage V_(CELL-EFF) may decrease accordingly.Therefore, maximum allowable current I_(PMAX) corresponding to maximumpower P_(MAX) may be a function of voltage V_(CELL-EFF) and impedancesof power delivery network 10.

In addition to limiting current to provide for protection of battery 12as described above, and in addition to limiting current to providestability for power converter 20 as described above, it may also oralternatively be desirable to limit current based on considerations ofpractical implementations, as described in greater detail below.

As an example, beyond a certain voltage V_(CELL-EFF), the maximumbattery current I_(CELL), and therefore the maximum power deliverycapability P_(MAX), of power converter 20 may become so large that thedesign of power converter 20 becomes increasingly difficult or evenunfeasible. Practical limitations such as, for example, inductorsaturation current and required dynamic range of current sensingcircuitry in power converter 20 may dictate an upper power limit P_(LIM)be placed on output power P_(OUT). Thermal considerations may also needto be taken into consideration and may drive a need to limit maximumpower delivery from power converter 20.

Assuming output power P_(OUT) is limited to power limit P_(LIM), a powerbalance equation for power delivery system 10 may be written as:

I _(CELL) ² R _(TOT) −I _(CELL) V _(CELL-EFF) +P _(LIM)=0

which can be rewritten as:

$I_{{C{ELL}} - {LIM}} = {I_{PMAX} - \sqrt{\frac{P_{MAX} - P_{LIM}}{R_{TOT}}}}$

This maximum allowable current I_(CELL-LIM) may be plotted as shown inFIG. 10 as constraint CON3A superimposed over constraints CON1 and CON2depicted in FIG. 9. A separation between two power limited regions forP_(MAX) and P_(LIM) are graphically shown in FIG. 10 as occurring at abreakpoint between the curves representing constraints CON2 and CON3A.In the region limited by power limit P_(LIM), a maximum for batterycurrent I_(CELL) may be set by the lower of the two values for maximumallowable current. As is shown in FIG. 10, along the curve forconstraint CON3A, the maximum current for battery current I_(CELL) mayincrease as voltage V_(CELL-EFF) decreases.

In addition to limiting current to provide for protection of battery 12as described above, limiting current to provide stability for powerconverter 20 as described above, and limiting current for power limitingconsiderations, it may also or alternatively be desirable to apply afixed current limit I_(FIXED) based on considerations of practicalimplementations, as described in greater detail below. This maximumallowable current I_(FIXED) may be plotted as shown in FIG. 11 asconstraint CON3B superimposed over constraints CON1, CON2, and CON3Adepicted in FIG. 10. Thus the maximum current for battery currentI_(CELL) may be set by the lowest of the four values for maximumallowable current.

As used herein, when two or more elements are referred to as “coupled”to one another, such term indicates that such two or more elements arein electronic communication or mechanical communication, as applicable,whether connected indirectly or directly, with or without interveningelements.

This disclosure encompasses all changes, substitutions, variations,alterations, and modifications to the example embodiments herein that aperson having ordinary skill in the art would comprehend. Similarly,where appropriate, the appended claims encompass all changes,substitutions, variations, alterations, and modifications to the exampleembodiments herein that a person having ordinary skill in the art wouldcomprehend. Moreover, reference in the appended claims to an apparatusor system or a component of an apparatus or system being adapted to,arranged to, capable of, configured to, enabled to, operable to, oroperative to perform a particular function encompasses that apparatus,system, or component, whether or not it or that particular function isactivated, turned on, or unlocked, as long as that apparatus, system, orcomponent is so adapted, arranged, capable, configured, enabled,operable, or operative. Accordingly, modifications, additions, oromissions may be made to the systems, apparatuses, and methods describedherein without departing from the scope of the disclosure. For example,the components of the systems and apparatuses may be integrated orseparated. Moreover, the operations of the systems and apparatusesdisclosed herein may be performed by more, fewer, or other componentsand the methods described may include more, fewer, or other steps.Additionally, steps may be performed in any suitable order. As used inthis document, “each” refers to each member of a set or each member of asubset of a set.

Although exemplary embodiments are illustrated in the figures anddescribed below, the principles of the present disclosure may beimplemented using any number of techniques, whether currently known ornot. The present disclosure should in no way be limited to the exemplaryimplementations and techniques illustrated in the drawings and describedabove.

Unless otherwise specifically noted, articles depicted in the drawingsare not necessarily drawn to scale.

All examples and conditional language recited herein are intended forpedagogical objects to aid the reader in understanding the disclosureand the concepts contributed by the inventor to furthering the art, andare construed as being without limitation to such specifically recitedexamples and conditions. Although embodiments of the present disclosurehave been described in detail, it should be understood that variouschanges, substitutions, and alterations could be made hereto withoutdeparting from the spirit and scope of the disclosure.

Although specific advantages have been enumerated above, variousembodiments may include some, none, or all of the enumerated advantages.Additionally, other technical advantages may become readily apparent toone of ordinary skill in the art after review of the foregoing figuresand description.

To aid the Patent Office and any readers of any patent issued on thisapplication in interpreting the claims appended hereto, applicants wishto note that they do not intend any of the appended claims or claimelements to invoke 35 U.S.C. § 112(f) unless the words “means for” or“step for” are explicitly used in the particular claim.

1. A portable electronic device, comprising: one or more components; abattery; a power converter configured to electrically couple to andreceive power from the battery and further configured to supplyelectrical energy to the one or more components; and control circuitryconfigured to: select a constraint factor from a plurality of differentconstraint factors based on at least one of an input voltage to thepower converter and a power level available to the power converter; andcontrol the power converter in accordance with the constraint factor. 2.The portable electronic device of claim 1, wherein: the controlcircuitry is configured to select the constraint factor based on avoltage level available from the battery.
 3. The portable electronicdevice of claim 2, wherein the control circuitry models the voltagelevel available from the battery as a time-varying voltage source inseries with an equivalent resistance.
 4. The portable electronic deviceof claim 2, wherein: a plurality of constraint regions are defined fordifferent ranges of the voltage level available from the battery; andthe control circuitry is configured to select the constraint factorbased on a constraint region of the plurality of constraint regionscorresponding to the voltage level available from the battery.
 5. Theportable electronic device of claim 4, wherein a first constraint regionof the plurality of constraint regions is associated with a firstconstraint factor which corresponds to a battery-imposed limitation onmaximum current.
 6. The portable electronic device of claim 5, whereinthe first constraint region commences at a critical end-of-dischargevoltage for the battery.
 7. The portable electronic device of claim 5,wherein the first constraint factor sets a maximum current limit for thepower converter defined by:$I_{{CELL} - {MAX}} = \frac{V_{{CELL} - {EFF}} - V_{{C{ELL}} - {MIN}}}{R_{0}}$where V_(CELL-EFF) is an effective battery voltage at a given instance,V_(CELL-MIN) is the critical end-of-discharge voltage for the battery,and R₀ is an equivalent series resistance of the battery.
 8. Theportable electronic device of claim 4, wherein a second constraintregion of the plurality of constraint regions is associated with asecond constraint factor which corresponds to a power converterstability-imposed limitation on maximum current.
 9. The portableelectronic device of claim 8, wherein the second constraint factor setsa maximum current limit for the power converter defined by:$I_{PMAX} = \frac{V_{{CELL} - {EFF}}}{2\left( {R_{0} + R_{TRACE} + R_{SNS} + R_{LOSS}} \right)}$where R₀ is an equivalent series resistance of the battery, R_(TRACE) isa resistance of a trace and/or connector resistance between the powersource and the power converter, R_(SNS) is a resistance of a currentsense resistor, and R_(LOSS) is a resistance modeling losses of thepower converter.
 10. The portable electronic device of claim 8, wherein:a first constraint region of the plurality of constraint regions isassociated with a first constraint factor which corresponds to abattery-imposed limitation on maximum current; and the second constraintregion commences at an intersection of the first constraint factor andthe second constraint factor.
 11. The portable electronic device ofclaim 4, wherein a third constraint region of the plurality ofconstraint regions is associated with a third constraint factor whichcorresponds to an output-power-based limitation on maximum current. 12.The portable electronic device of claim 11, wherein the third constraintfactor sets a maximum current limit for the power converter defined by:$I_{{C{ELL}} - {LIM}} = {I_{PMAX} - \sqrt{\frac{P_{MAX} - P_{LIM}}{R_{0} + R_{TRACE} + R_{SNS} + R_{LOSS}}}}$where I_(PMAX) is a maximum current limit as defined for a secondconstraint factor, P_(MAX) is a maximum power delivery capability of thepower converter, P_(LIM) is an output power limit defined for the powerconverter, R₀ is an equivalent series resistance of the battery,R_(TRACE) is a resistance of a trace and/or connector resistance betweenthe power source and the power converter, R_(SNS) is a resistance of acurrent sense resistor, and R_(LOSS) is a resistance modeling losses ofthe power converter.
 13. The portable electronic device of claim 12,wherein a second constraint region of the plurality of constraintregions is associated with the second constraint factor whichcorresponds to a power converter stability-imposed limitation on maximumcurrent.
 14. The portable electronic device of claim 11, wherein: asecond constraint region of the plurality of constraint regions isassociated with a second constraint factor which corresponds to a powerconverter stability-imposed limitation on maximum current; and the thirdconstraint region commences at a breakpoint between the secondconstraint factor and the third constraint factor.
 15. The portableelectronic device of claim 4, wherein a fourth constraint region of theplurality of constraint regions is associated with a fourth constraintfactor which corresponds to a fixed current limit.
 16. The portableelectronic device of claim 4, wherein: a second constraint region of theplurality of constraint regions is associated with a second constraintfactor which corresponds to a power converter stability-imposedlimitation on maximum current; a third constraint region of theplurality of constraint regions is associated with a third constraintfactor which corresponds to an output-power-based limitation on maximumcurrent; and a fourth constraint region is located between the secondconstraint region and the third constraint region.
 17. The portableelectronic device of claim 4, wherein the plurality of constraintregions includes: a first constraint region associated with a firstconstraint factor which corresponds to a battery-imposed limitation onmaximum current; a second constraint region with a second constraintfactor which corresponds to a power converter stability-imposedlimitation on maximum current; a third constraint region associated witha third constraint factor which corresponds to an output-power-basedlimitation on maximum current; and a fourth constraint region associatedwith a fourth constraint factor which corresponds to a fixed currentlimit.
 18. The portable electronic device of claim 1, wherein theconstraint factor defines a current limit to be drawn from the battery.19.-43. (canceled)
 44. The portable electronic device of claim 1,wherein the one or more components comprise at least one of thefollowing: another power converter, a processor, an audio coder/decoder,an amplifier, and a display device.
 45. The portable electronic deviceof claim 1, wherein the battery comprises a lithium-ion battery.
 46. Theportable electronic device of claim 1, wherein the power converter isimplemented using at least one of a boost converter, buck converter,buck-boost converter, transformer, or charge pump.
 47. The portableelectronic device of claim 1, wherein the portable electronic devicecomprises a smart phone, a tablet, or a game controller.
 48. A portableelectronic device comprising: one or more components; a battery; a powerconverter configured to electrically couple to and receive power fromthe battery and further configured to supply electrical energy to theone or more components; and control circuitry configured to: calculate aplurality of current limit values based on at least one of an inputvoltage to the power converter and a power level available to the powerconverter; and control the power converter based on a current limitselected as a lowest of the plurality of current limit values.
 49. Theportable electronic device of claim 48, wherein the one or morecomponents comprise at least one of the following: another powerconverter, a processor, an audio coder/decoder, an amplifier, a displaydevice.
 50. The portable electronic device of claim 48, wherein thebattery comprises a lithium-ion battery.
 51. The portable electronicdevice of claim 48, wherein the power converter is implemented using atleast one of a boost converter, buck converter, buck-boost converter,transformer, or charge pump.
 52. The portable electronic device of claim48, wherein the portable electronic device comprises a smart phone, atablet, or a game controller.
 53. A power delivery system comprising: apower converter configured to electrically couple to a power source andfurther configured to supply electrical energy to one or more loadselectrically coupled to an output of the power converter; and controlcircuitry configured to: calculate a plurality of current limit valuesbased on at least one of an input voltage to the power converter and apower level available to the power converter; and control the powerconverter based on a current limit selected as a lowest of the pluralityof current limit values.
 54. The power delivery system of claim 53,wherein the one or more loads comprise at least one of the following:another power converter, a processor, an audio coder/decoder, anamplifier, a display device.
 55. The power delivery system of claim 53,wherein the power source comprises a battery.
 56. The power deliverysystem of claim 55, wherein the battery comprises a lithium-ion battery.57. The power delivery system of claim 53, wherein the power converteris implemented using at least one of a boost converter, buck converter,buck-boost converter, transformer, or charge pump.
 58. A methodcomprising, in a power converter configured to electrically couple to apower source and further configured to supply electrical energy to oneor more loads electrically coupled to an output of the power converter:calculating a plurality of current limit values based on at least one ofan input voltage to the power converter and a power level available tothe power converter; and controlling the power converter based on acurrent limit selected as a lowest of the plurality of current limitvalues.
 59. The method of claim 58, wherein the one or more loadscomprise at least one of the following: another power converter, aprocessor, an audio coder/decoder, an amplifier, a display device. 60.The method of claim 58, wherein the power source comprises a battery.61. The method of claim 60, wherein the battery comprises a lithium-ionbattery.
 62. The method of claim 58, wherein the power converter isimplemented using at least one of a boost converter, buck converter,buck-boost converter, transformer, or charge pump.